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The Brown Bullhead Catfish in New Zealand
This harmful fish doesn't belong here and is causing trouble for New Zealand's natural water places.
How They Got Here
Their Home in America
Brown Bullhead Catfish come from North America. You can find them in the eastern and middle parts of the United States and southern Canada. For hundreds of years, people there, like the Native Americans, ate them. They were an important part of the local natural environments. These fish were taken to Europe a long time ago, in the 1800s. From there, they spread to many other places around the world.
Coming to New Zealand
Brown Bullhead Catfish were brought to New Zealand in the 1870s. People wanted them for fun fishing and to eat. They were brought because they are tough fish and can live well in many different freshwater places. However, some escaped or were let go into the rivers and lakes. They started making families there and became harmful fish that don't belong here.
What Catfish Look Like
Size and Weight
These catfish can grow up to 50 centimeters long. They can weigh as much as 1.8 kilograms.
Body Shape
They have a strong, long body. Their skin is smooth and does not have scales, like many other fish.
Color
Their color is usually dark brown or black on top. Their bellies are a lighter color.
Special Features
They have whisker-like feelers around their mouth. These feelers help them explore and find food in the water.
The Catfish Story: From Egg to Adult
Making Nests
Female catfish build nests in shallow water that has many plants. This is where they lay their eggs.
Eggs Hatch
Male catfish make the eggs ready to grow. These eggs then hatch into tiny baby fish in about a week.
Growing Up
The tiny baby fish eat very small creatures. As they get older, they slowly start to eat different kinds of food.

Making More Catfish: A single female catfish can have up to 6,000 babies in one season. This helps their numbers grow quickly.
What Catfish Eat
Brown Bullhead Catfish eat both plants and animals. They munch on algae, water plants, bugs, small crabs, tiny fish, and even bits of dead stuff. These fish can easily change what they eat, which helps them live well in many different water places like rivers and lakes. This also helps them become harmful fish that don't belong here in many places, such as New Zealand.
Plants
They eat algae and water plants.
Small Creatures
They find bugs, small crabs, and snails using their whiskers.
Smaller Fish
They also hunt and eat smaller fish, taking food away from fish that naturally live there.
Why Catfish Can Be a Problem
In New Zealand, Brown Bullhead Catfish are seen as a harmful fish that doesn't belong there. They cause big problems for the natural environments where local plants and animals live. These catfish often live in calm rivers, lakes, and ponds. They stir up the mud at the bottom, pull up water plants, and take food and homes away from the fish that naturally live there. This makes the natural homes worse for other creatures.
"These catfish can live in many different water places because they are tough and can get used to different conditions. They eat other animals and use their long whiskers to find food like bugs, small crabs, and little fish at the bottom of the water. They even eat Koura (New Zealand crayfish) and other special local animals. They can live in dirty water and make it even dirtier when they look for food, stirring up the mud. A female catfish can have up to 6,000 babies in one year!"
— Bay of Plenty Regional Council
How Catfish Harm Our Natural Environments
Messing Up Homes
Catfish stir up mud and pull up underwater plants. This ruins important homes for the animals and plants that belong here.
Fighting for Food and Homes
They take food and homes from fish that belong here. This means there are fewer kinds of plants and animals in our natural fresh water.
Eating Special Animals
Catfish eat Koura (freshwater crayfish) and other animals that are very special to our culture.
Making Water Dirty
When catfish eat from the bottom, they stir up mud and dirt. This makes the water dirty and cloudy.
Easy to Live Anywhere and Spread
Tough Fish
Brown Bullhead Catfish can live in dirty water. They can survive in many different places, which means they can start living in almost any river, lake, or pond across New Zealand.
They eat other animals and use their whiskers (called barbels) to find food at the bottom. This makes them very good hunters. Since they also have many babies, they can grow fast and spread quickly in freshwater natural environments.
6K
Babies Each Year
They can have many babies quickly.
50cm
How Long They Grow
They can get quite big!
Control and Management Efforts
Efforts to control Brown Bullhead Catfish populations in New Zealand include various methods aimed at reducing their impact on native ecosystems. These measures are essential to protect native species and restore the balance of freshwater habitats.
01
Trapping
Targeted trapping programmes to remove catfish from affected waterways
02
Netting
Use of specialised nets to capture catfish populations in lakes and ponds
03
Habitat Modification
Altering environments to make them less suitable for catfish whilst supporting native species
04
Monitoring
Ongoing surveillance to track populations and assess control effectiveness
Key Questions About Brown Bullhead Catfish
Origins
Where do Brown Bullhead Catfish originate from, and how long have they been part of local ecosystems there?
Answer: They originate from eastern and central United States and southern Canada, where they have been integral to ecosystems for centuries.
Introduction to NZ
When and why were Brown Bullhead Catfish introduced to New Zealand?
Answer: They were introduced in the 1870s for recreational fishing and as a food source.
Ecological Concerns
What are the ecological concerns associated with their establishment in New Zealand?
Answer: They disturb sediment, uproot vegetation, outcompete native fish, prey on taonga species, and contribute to water quality decline.
Physical Characteristics
Describe their physical characteristics and growth potential.
Answer: They grow up to 50cm and 1.8kg, with stout bodies, smooth scaleless skin, dark brown or black coloration, and distinctive barbels.
Impact and Control
What impact do they have on freshwater ecosystems and what control measures are being taken?
Answer: They degrade habitats and outcompete native species. Control measures include trapping, netting, and habitat modification.
Answer Key
  1. Brown Bullhead Catfish originate from North America, where they’ve long been part of local ecosystems and traditional food systems.
  1. They were introduced to New Zealand in the 1870s for recreational fishing and food, due to their hardiness.
  1. Once established, they disturb sediment, uproot plants, and outcompete or prey on native species, causing freshwater habitat degradation.
  1. They grow up to 50 cm and about 1.8 kg, with scaleless dark brown/black bodies and distinctive whisker-like barbels.
  1. In New Zealand they muddy waterways, eat native fish and koura, and compete for habitat. Control efforts include trapping, netting, and habitat management.